The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Known engine operation includes delivering fuel and air to combustion chambers and igniting the corresponding mixture, and transferring the pressure generated by the ignited mixture to a crankshaft via a moveable piston. Engine operating parameters of interest include in-cylinder pressure, engine torque, specific fuel consumption, emissions, and others. Engine control parameters include fuel mass and injection timing, spark ignition timing in spark ignition engines, phasing, magnitude and duration of engine valve opening and closing, recirculated exhaust gas fraction, and other parameters. Known engine control schemes include monitoring states of engine operating parameters and controlling engine control parameters to achieve preferred targets corresponding to in-cylinder pressure, engine torque, specific fuel consumption, and emissions.
It is known to control combustion in individual cylinders using data corresponding to in-cylinder combustion parameters. One exemplary in-cylinder combustion parameter includes location of peak cylinder pressure (LPP) in crank angle degrees, which is an indicator of peak in-cylinder combustion pressure. In-cylinder pressure sensors monitor in-cylinder pressures for individual cylinders during ongoing engine operation, and are coupled to signal processing devices. Known engine control schemes use the monitored in-cylinder pressures for individual cylinders to control engine control parameters including, e.g., spark timing, fuel injection timing, and EGR mass flowrate.
Another exemplary in-cylinder combustion parameter is a location of mass-burn fraction (MBF), which is an estimate of percentage of a cylinder charge that is combusted at a given crank angle. One mass-burn fraction of interest is a 50% mass-burn fraction (CA50), which is a crank angle location at which 50% of an individual cylinder charge is burned.
Monitoring the 50% mass-burn fraction is one known method to parameterize combustion phasing for a cylinder. During engine combustion operating under a particular set of parameters, the 50% mass-burn fraction is predictable to within a small range for given engine operating conditions. One known method to estimate the 50% mass-burn fraction includes examining pressure data from within the combustion chamber, including analyzing the pressure rise within the combustion chamber attributable to combustion. Various methods exist to quantify pressure rise in a combustion chamber attributable to combustion. One method includes pressure ratio management (PRM) which is based upon the Rassweiler approach, which approximates the 50% mass-burn fraction by a fractional pressure rise due to combustion. Combustion of a known charge at a known time under known conditions tends to produce a consistently predictable pressure rise within the combustion chamber. PRM derives a pressure ratio from the ratio of a measured cylinder pressure under combustion at a given crank angle to a calculated motored pressure, estimating a pressure value if no combustion took place in the cylinder, at a given crank angle. Any rise in pressure above the motored pressure is attributable to energy introduced by combustion. Thus, PRM can be used to describe the combustion process within a cylinder, including combustion phasing information, with the pressure ratio value normalized at a given crank angle, and a fractional pressure ratio useful for estimating the 50% mass-burn fraction.
Known engine control schemes include monitoring peak cylinder pressure (LPP) in crank angle degrees, which is an indicator of peak in-cylinder combustion pressure. In-cylinder pressure sensors coupled to signal processing devices are used during ongoing engine operation to monitor in-cylinder pressures for individual cylinders. Known engine control schemes use the monitored in-cylinder pressures for individual cylinders to control engine control parameters including, e.g., spark timing, fuel injection timing, and EGR mass flowrate.